An exemplary refrigeration system, designed for cooling only, is disclosed in J. H. Perry, CHEMICAL ENGINEER'S HANDBOOK (4th Edition New York 1963) at pages 12-10 thru 12--12. A generator is provided with an inlet for a rich or strong liquor (absorbent with a high concentration of refrigerant). The rich liquor contains water (the "absorbent" or solvent) and a high concentration of ammonia (the refrigerant or "solute"). The rich liquor is heated and separated into refrigerant vapor and a "weak" liquor or aqua (absorbent with a low concentration of refrigerant). The gaseous ammonia refrigerant passes under pressure to a condenser where it is condensed by heat exchange with a first cold water coil and then flows through an expansion valve. The liquid ammonia is then evaporated in an evaporator in heat exchange relation with a second coil which communicates with a cold storage room or ice tank and contains a circulating coolant such as brine. The evaporated ammonia then passes to an absorber where it mixes with weak liquor from the generator, evolving heat, some of which is removed by a third coil containing circulated water.
In such a system the rich liquor is pumped from the rich liquor outlet of the absorber to the rich liquor inlet of the generator via an enclosure denominated a heat exchanger. Weak liquor from the weak liquor outlet passage of the generator passes through a fourth coil in the heat exchanger to the weak liquor inlet of the absorber. Heat is transferred only from the weak liquor to the strong liquor, out of the coolant in the second coil and into the coolants of the first and third coils. In the refrigeration system described, the heat taken into the first and third coils is rejected to "waste" or the atmosphere.
Other heat activated, absorption refrigeration systems as well as some heat pumps are disclosed in U.S. Pat. Nos. 2,193,535 (Mar. 12, 1940 to Maiuri), 2,201,362 (May 21, 1940 to Bergholm), 2,392,894 (Jan. 15, 1946 to Zwickl), 3,236,064 (Feb. 22, 1966 to Whitlow), 3,270,523 (Sept. 6, 1966 to McNeely), 3,509,732 (May 5, 1970 to Roeder, Jr.), 3,516,264 (June 23, 1970 to Stierlin), 3,527,060 (Sept. 8, 1970 to Kruggel), 3,638,452 (Feb. 1, 1972 to Kruggel).
Although absorption systems have been proposed for many years, it is not believed that any have been successfully commercialized with the capability of operating in the heating mode. Many have failed to maintain the high temperature differentials in the system, and thus the high concentration differentials between rich and weak liquor desirable for efficient operation. This inadequate efficiency and capacity is most noticeable at cold ambient air conditions below 32.degree. F. (0.degree. C.), but has some effect as well under milder heating conditions or under air conditioning conditions.